The present invention relates to a valve model for an artificial urinary sphincter to be placed intraurethrally in humans, which performs the functions of the external urinary sphincter, meant for treating urinary incontinence and/or retention. Opening of said valve is controlled from outside the human body by the application of a magnetic field created by a permanent magnet. The valve is closed automatically by a permanent magnet placed inside the valve.
The purpose of the present invention is the recovery of self-control of urination for those people who have lost it by means of an easily implanted prosthesis.
Hitherto, people suffering from urinary incontinence or retention deal with said problem with soakers, or probes provided with urine collection bags. The former is uncomfortable and causes serious social problems, while the latter often causes infections, often with a fatal outcome due to kidney failure. Work has been directed for some time towards designing prostheses which may replace the function of the urinary sphincter, although there is none yet in widespread use.
There exist some prosthesis which involve voluntary strangulation of the urethra (U.S. Pat. No. 3,744,063, U.S. Pat. No. 3,854,469, U.S. Pat. No. 3,903,849, EP0314258). The one used most has been commercialized under the name AMS-800 of American Medical System. Implantation of this type of prosthesis requires invasive surgery. Additionally, the firm Uroquest has developed a system to fight urinary incontinence consisting of a probe with an outlet orifice at the end of the urethra, but which does not reach the exterior and which is opened by means of an external magnet.
The device object of the present invention allows control of urination by the patient and may be implanted without need of surgery by cytoscopy.
The external magnetically actuated valve for an artificial intraurethral urinary sphincter is, in essence, a fluid cut-off valve with an attachment system similar to that used in urethral probes, which can be implanted by cytoscopy.
The valve is essentially comprised of:
a hollow cylindrical body, made of a biocompatible material (e.g. Teflon), constituting the valve body, with an inlet sector and an outlet sector communicated by a central orifice, so that it can be crossed by a fluid.
a piston that can slide inside the outlet sector of the cylindrical body, made of a soft magnetic material (e.g. Fexe2x80x94Si 3%) and coated with a biocompatible material (e.g. Teflon). One of its ends has a cone or sphere shape to improve the seal of the central orifice.
an internal permanent magnet (e.g. NdFeB), toroidal in shape and magnetically hard, coated with a biocompatible material (e.g. Teflon) disposed in the inlet sector of the cylindrical valve body.
The valve operation is as follows:
The internal permanent magnet exerts an attractive force on the internal piston until the conical or hemispherical end of the piston covers the central orifice of the cylindrical body, closing the valve. An external permanent magnet is used to open the valve. When said external permanent magnet is approximated from outside the person""s body to the area where the valve is implanted it exerts a greater force on the piston than that exerted by the internal permanent magnet, in the opposite sense, due to the reorientation of the magnetic moment of the piston, opening the valve and allowing urine to exit. When the external permanent magnet is removed the force of the internal permanent magnet on the piston makes it close again the central orifice, cutting off the outwards flow of urine.
The valve is also provided with a safety system based on the fact that the force exerted by a magnet on a ferromagnetic object, the piston in this case, falls rapidly with the distance between them. More specifically, when the urine reaches a threshold pressure the piston is separated, so that the force exerted by the internal magnet on the piston falls and the piston will be displaced until the valve is fully opened. This allows ensuring that when it is not possible to apply an external magnetic field for any reason the pressure in the bladder will never exceed a certain value, preventing damage to the urinary system due to excess pressure in the bladder.